Vehicles which are adapted to support a load from one end thereof are in common usage. Typical of such vehicles are "front end loaders" and "fork lifts" both of which have mechanisms attached thereto for engaging and lifting a load. It has been appreciated with front end loaders, for example, that the front opening excavating bucket is perferably propelled into the material while the tires of the vehicle are stationary. If the tires of the vehicle to which the bucket is attached are moving when the bucket encounters the material there will usually be slippage between the tire and the surface upon which the vehicle is operating causing rapid wear of the tires. Further, if the excavating bucket must be propelled into the material while the vehicle is moving the position of the bucket cannot be as accurately controlled as when the vehicle is stationary and the bucket is propelled by other means. Devices capable of extending the excavating bucket with the vehicle to which it is mounted remaining in a stationary position are illustrated in U.S. Pat. No. 3,327,880 issued to E. C. Brown on June 27, 1967, No. 2,707,059 issued to C. Gerst on Apr. 26, 1955, No. 2,820,555 issued to H. F. Lessmann on June 21, 1958, and Australian Pat. No. 167,063 issued to O. B. Holbrook on Feb. 21, 1956.
The prior mechanisms employed to propel an excavating bucket or the like into a material have, however, had certain disadvantages. They are complex to operate, expensive to maintain or unstable when operating in certain modes.